Selecting isolation level for an operation based on manipulated objects
Concurrency control overhead in transactional memory and main memory databases is reduced by automatically selecting the appropriate isolation level for each operation based on the objects accessed by the operation.
1 . A method of executing transactions in a computer, comprising:
selecting, by a transaction executing in the computer, the isolation level for an operation performed within the transaction based on the data manipulated by the operation.
2 . The method of claim 1 , wherein the selection is made at run time, at least in part based on the address of the data manipulated by the operation.
3 . The method of claim 1 , wherein the selection is made at run time based at least in part on a value read from an object comprising data manipulated by the operation.
4 . The method of claim 3 , further comprising:
determining the isolation level required for an object based on its connectivity with other objects, and storing information indicating the isolation level in the object.
5 . The method of claim 4 , further comprising:
determining the isolation level required for each field of an object based on the object's connectivity with other objects, and storing information indicating the isolation level in the object separately for at least two fields.
6 . The method of claim 4 , further comprising:
updating, in at least one case, the information indicating the isolation level of the object when its connectivity with other objects changes.
7 . The method of claim 1 , further comprising:
in response to the per-operation isolation level indicating that full serializability is not required, reading at least one object without creating a verification item for it.
8 . The method of claim 1 , further comprising:
having more than one write lock level for the same object, different values indicating different isolation levels for the object; and
in response to a write to the object, setting the write lock indicator for the object in accordance with the isolation level.
9 . A computer comprising:
a transactional memory facility
coupled to the transactional memory facility, a means for selecting the isolation level for an operation performed within a transaction based on one or more of the objects manipulated by the operation.
10 . The computer of claim 9 , wherein the means for selecting the isolation level selects the isolation level at run time based at least in part on a value read from an object comprising data manipulated by the operation.
11 . The computer of claim 10 , further comprising:
a means for determining the isolation level required for an object based on its connectivity with other objects and storing information about the isolation level in the object.
12 . A computer program product stored on a computer-readable medium operable to cause a computer to select the isolation level for an operation based on the data manipulated by the operation, comprising:
a computer readable program code means for implementing transactional memory
a computer readable program code means for selecting the isolation level used by the transactional memory for an operation performed within a transaction based on one or more of the objects manipulated by the operation.
13 . The computer program product of claim 12 , wherein the computer readable program code means for selecting the isolation level is responsive to a value read from an object comprising data manipulated by the operation.
14 . The computer program product of claim 13 , further comprising:
a computer readable program code means for determining the isolation level required for an object based on its connectivity with other objects and storing information about the isolation level in the object.